There is an increasing need for reliable bio-sample storage at temperatures ranging from room temperature (20 degrees C.) down to ULT as low as −150° degrees C. Since these bio-samples include sensitive tissues and vaccines for protecting against pan-epidemics that could break out naturally or by acts of terrorism, the insulation systems for their storage are required to not only develop the required low temperature, but to continuously maintain that temperature accurately and reliably since even temporary loss of cooling could weaken, damage or even destroy existing supplies of vaccines, etc. Many of such stored substances are precious, e.g. very costly and having been accumulated over a long period of time, thus requiring an extremely long time for replacement, so loss in storage could place large populations at risk.
The structure of the door(s) and load location in the enclosure are critical considering temporary temperature rise during time periods when the door is open for loading and unloading samples.